Supported Keggin-type

Other classes of catalysts investigated include supported Keggin-type P/Mo/V/O polyoxometalates [14-16], and titania-supported vanadium oxide or V/P/(Mo)/0... 

Pizzio, L., Vazquez, P., Caceres, C., Blanco, M. 2(X)3. Supported Keggin type heteropolycompounds for ecofriendly reactions. App/icrf Catalysis A General 256 125—129. 

New acid catalyst comprising Keggin-type heteropoly acid supported on mesoporous silica for dehydration of acetic acid... 

The selectivity for acetic anhydride in the catalytic dehydration of acetic acid could be controlled by the pore size of pure mesoporous silica SBA-15. New acid catalyst comprising Keggin-type heteropoly acid supported on SBA-15 enhanced the activity etfectively when tungstophosphoric acid was highly dispersed on the silica substrate. 

Keggin-type heteropoly compounds having Mo and V as addenda atoms are usually used for such oxidations. The catalysts reported in patents often contain several elements other than Mo, V, and P. An excess amount of P is added to stabilize the structure, and the presence of additional transition elements like Cu improves redox reversibility. Supported heteropoly catalysts are also important for industrial applications and have been characterized (69, 325, 326). 

Various Keggin-type polyoxometalates (POMs) were tested as catalysts for the ODS of gas oil with t-butyl hydroperoxide. Alumina-supported phosphomolybdic acid (H3PMoi2O40) proved to be quite active, yielding sulfur conversion higher than... 

Keggin-type heteropoly compounds have attractive and important characteristics in terms of catalysis. They consist of heteropolyanions and counter-cations such as H, Cs or NHT When the counter-cations are protons, they are called heteropolyacids (HPA). An important characteristic of HPAs, such as 12-tungstophos-phoric acid (H3PW12O40), is the presence of very strong Bronsted acid sites. But the characteristics of HPAs strongly depend on temperature and relative humidity. When they are used in heterogeneous catalysis, it is often necessary to support them on high-surface-area oxides or activated carbons, in order to increase the surface contact with the reactants. 

The effect of supporting Dawson-type and Keggin-type HPA on Si02 in the isomerisation of 1-butene. 

Mukai and co-workers [105] used Keggin-type heteropolyacids immobilized in the network structure of resorcinol-formaldehyde carbon gels as catalysts for the synthesis of methyl tert-butyl ether from methyl alcohol and tert-butyl alcohol. Large amounts of 12-tungstophosphoric and 12-molybdophosphoric acids were immobilized into the support by two methods, pore shrinkage and the ship-in-the-bottle method, which are essentially impregnation methods. The authors reported that these catalysts showed activity in the reaction studied and could be of practical utility as solid acid catalysts in various reactions. 

In the present work we describe the preparation and properties in ethanol conversion of conjugated polymer supported heteropolyanions of Keggin-type structure. Thus 12-molybdophosphoric acid (H3PM012O40) has been supported on polyacetylene (PAc)... 

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